Bulb (photography)

Detail of an old Kodak camera with shutter set to Bulb.

Bulb, abbreviated B, is a shutter speed setting on an adjustable camera that allows for long exposure times under the direct control of the photographer. With this setting, the shutter simply stays open as long as the shutter release button remains depressed. An alternative setting common on film cameras is Time, abbreviated T, where the button is pressed once to open the shutter and again to close it.

History

The term bulb is a reference to old-style pneumatically actuated shutters; squeezing an air bulb would open the shutter and releasing the bulb would close it. According to the Focal Encyclopedia of Photography:

BULB EXPOSURE (B). Another term for a brief exposure—in which the shutter remains open only so long as the shutter release is held down. The word originated with the early pneumatic shutter release.

It is not clear when the term actually originated. It appears that when instantaneous shutters were introduced, they included a B setting so that the familiar bulb behavior could be duplicated with a cable release. This may have been the origin of the term bulb in reference to shutter settings. (See the photo captions.)

Use

The bulb setting is used on some cameras, including some point-and-shoot cameras, to obtain shutter speeds slower than the maximum offered by the camera otherwise.

Because of the risk of camera movement, the camera is most often mounted on a tripod for the duration of the exposure. While it's generally possible to use the shutter release button on the camera itself, a cable release or electronic remote is often used to further eliminate the risk of shaking the camera during the long exposure. The cable releases generally include a locking feature to eliminate the need to keep the button or plunger depressed during extremely long exposures.

The bulb setting is useful for the following types of photographic subjects:

• fireworks at night
• the night sky and celestial objects (see astrophotography)
• lightning
• streets at night (creating streaks from moving cars)

On modern cameras

On some modern cameras, bulb is a mode available as an option on the LCD menu only, if possible at all. On others, including many Digital SLR cameras, bulb is available from the manual exposure mode or shutter priority modes.

When set to bulb, generally on the "M" or manual setting of the camera, the shutter will stay open as long as the shutter release button (or shutter release cable or remote) remains depressed.

Some mid-level or bridge cameras such as the Olympus SP-560UZ have a 'limited' bulb setting, allowing time exposures up to 8 minutes and at an ISO setting of 200 ISO and lower.^{[citation needed]}

Some specialized cameras use other image triggers.

Gallery

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  Circa 1894 page showing a camera with an "indiarubber ball" and a "time exposure" mode that works like what came to be called "bulb". Suggests that the "bulb" terminology had not yet been introduced.

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  1898 Bausch & Lomb ad showing a shutter with B setting; the explanation displayed "bulb exposure" in quotation marks and explained it in detail, since the term was still novel.

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  A more modern (circa 1950) camera cable release.

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  Photo shot with a Bulb exposure. The movement of the clouds, crossing arms and passing train register as streaks rather than sharp images, unlike the stationary objects in the frame.